Reading electronic schematicsMade by Miguel Dräger (@Bl4ckM4ch1n3)
A quick guide about understanding schematics
Electronic schematics can be confusing at first but are actually pretty easy to master.
Having the ability to read them properly might come in handy when assembling any of your electronic projects.
Also, electronic schematics are very important if you’re working on an electronic device as you need to draw the schematic first before you move on to circuit board design.
First of all, there is a difference between reading a schematic and understanding a schematic.
To understand it, you’ll need some knowledge related to basic electronic components and how they work together in electronic circuits.
In order to read the schematic, you’ll just have to follow a few basic rules.
You can see the full electronic schematic of MAKERbuino below:
MIND THE LINES!
Let’s start with the basics of a schematic.
The lines between different electronic components represent electrical connections (wires or copper traces on a PCB).
Also, as you can see in the following picture, there are two different kinds of crossing lines – the ones without a dot and the ones with a dot.
If there are two lines crossing each other and there is no dot (like the blue marked example) there is no connection between those lines (or signals).
If there are two lines crossing each other and there is a black dot, then those lines (or signals) are connected. Check the arrows to see how the signals are flowing. This is, of course, a pretty brief example, not the actual flow of current.
Next, there are those weird flag-like symbols with some text written on them.
They are called Ports. You’ll use ports to avoid drawing a full connection line all over the schematic as this will make your schematic really messy.
Ports with the same name are sharing the same signal/connection as you can see in the following picture.
Same goes for voltages and power supply symbols (such as the positive voltage source marked “VCC” and the negative voltage source markeg “GND” – which stands for “GROUND”).
These marked symbols work like ports but they look different.
The symbols can differ a little bit, depending on which software you use to create your schematics.
In example: the upward arrow of VCC could also be a circle and the GND symbol could look like a three-legged fork (for example).
As we already mentioned, those work like ports. This makes it very easy to clean up your schematic as you won’t need to draw a connection line between every single component and their power supply.
The last part of this guide will cover the different voltages/signals.
Both, VDD and VCC, are describing a positive voltage such as +3.3V or +5V (common values for many digital circuits).
ONCE UPON A TIME… MAKERbuino runs at 3.3V
MAKERbuino’s logic (microcontroller, SD card, input buttons, all the “SMART stuff”) runs at 3.3V.
MAKERbuino is powered by a li-po battery that has a nominal voltage of 3.7V (which can go up to 4.1V when full charged).
Unfortunately, MAKERbuino’s “SMART stuff” cannot tolerate the voltage as high as 3.7V and that’s why we have to use a voltage regulator and feed the “SMART stuff” with a stable, regulated 3.3V power source.
On the other side, VEE and VSS are describing a negative voltage but they are often identical to GND (ground).
GND stands for ground and you can think of it as a power source that has 0V all the time.
This is because the voltage is a difference in electric potential energy between two points (you heard that in school, don’t lie to us!).
So, if you’re measuring voltage with a multimeter you’re basically measuring the difference between two measurement points (mostly GND and VCC).
Oh yes, MAKERbuino has something marked VBAT too!
This is simply the voltage supplied by the battery. We’ve marked it this way in order to simplify the schematic a bit more.
The difference between VBAT and VDD/VCC is that the voltage from BAT is unregulated and therefore not constant. This is why the MAKERbuino needs a voltage regulator (IC2 if you look at the schematic). It provides 3.3V constantly, which is important when it comes to supplying chips (the “SMART stuff” mentioned earlier).
Everything inside your MAKERbuino uses the regulated VCC/VDD except for three things: The display, the Stereo jack and the breakout pins. Why is this so… we’ll cover it in another article soon.
As you can see in the picture above, unregulated VBAT is marked with a red circle and regulated VCC is marked with a blue “circle”.
And that would be it!
You’re an electronics guru now and we can feel it. You’d better start your hardware startup ASAP!
Call us if you need any help with that 🙂